1. Field of the Invention
The present invention generally relates to hardcopy apparatus, such as copiers, printers, scanners, and facsimiles, and more particularly to improved media advancing devices for such apparatus.
2. Description of the Prior Art
In hardcopy apparatuses and particularly in apparatuses handling media of large size, such as large format printers, a printed medium is fed to the printer from a roll of medium, the roll of medium being submitted to a braking force in order to ensure that a back-tension is maintained on the medium in order to avoid misalignments which may be caused by loose medium feeding. Conventional braking devices use a friction torque for this purpose, employing for example a braking shoe applying a predetermined braking force such as disclosed in EP 0 905 072 A1 in order to apply such a friction torque.
The friction torque is dependent on the amount of braking force applied, but also on the coefficient of friction at the zone of friction considered. The coefficient of friction itself is highly dependent on the type of medium used as well as on the conditions at the zone of friction. During use, it is for example common that dirt gets deposited at the zone of friction, for example. The consequence is that the friction torque varies which in turn means that the back-tension on the roll of media can become inappropriate.
An object of the present invention is to achieve a braking effect which remains significantly constant over time and usage and hence provide a predictable tension of the medium regardless of the variation of the coefficient of friction at the zone of friction on the roll.
The present invention provides an improved method of feeding a medium as well as an improved medium feeding system.